Gameobject prefab, when painted as a tree on terrain, shows shadow artifacts on zooming out when billboard starts to draw

Steps to Repro:
1. Open the attached project or create a new project
2. Hierarchy > right click
3. 3D Object > cube
4. Set Cube scale to 10,10,10
5. Drag the cube in the project window to create a prefab
6. 3D Object > terrain
7. Select 'paint tree' tab on terrain > edit tree > add tree
8. Add cube prefab as a tree
9. Paint it on terrain

Actual Result:
1. Shadow artifacts appear on the terrain when zoomed out
2. Cube used as tree keeps the scale (1,1,1) when its painted on terrain, however, when zoomed out the billboards are scaling according to the scale of cube's prefab

Expected result:
1. Billboards should render smoothly and shadow artifacts shouldn't appear
2. When a game object is painted as a tree, billboards should maintain it's scale.

Environment:
Windows and Mac

Occurring with:
2018.3.0a11, 2018.2.0f2, 2018.1.6f1 ,2017.4.9f1, 2017.3.1p4, 2017.2.3p4

Working with:
2017.1.5f1